1. Field of the Invention
The present invention relates to a container of sheet metal including a wall whose ends are connected by means of a fold to a bottom wall and/or a top wall. Each fold is additionally reinforced, secured and/or sealed by soldering and/or by welding.
2. Description of the Prior Art
It is basically known in the art to connect bottom walls and/or top walls of containers to the side walls thereof by means of folds or by means of welding. When folds are used, it may be necessary to seal the folds by applying a sealing agent on the portions of the walls to be folded. In the manufacture of containers of tin sheet, it is also known to seal the folds by means of soldering.
Moreover, it is known from German Offenlegungsschrift No. 35 46 458, in the manufacture of containers of the above-described type, to connect at least two of the layers of the fold after the fold has been finished by means of fusion welding at least at some locations in order to improve the strength of the fold and, in the case of continuous welding, the tightness of the fold.
However, it has been found that, in the case of fusion welding seams made by laser beams in folds, frequently the desired reinforcement of the mechanical connection and the desired absolute tightness of the container are not ensured.
As described in German Offenlegungsschrift No. 35 46 458, at least two, preferably three, layers of the sheet metal are welded together. However, in many regions of a fold, the layers of sheet metal forming the fold are not located directly one on top of the other, but rather they are separated from each other by an air gap, so that a laser beam can melt the individual layers, but these layers cannot be connected with each other. In this connection, it cannot even be assumed that such gap-like hollow spaces within a fold are present only at certain locations because, even when the containers are carefully manufactured and the folds are prepared by exact folding devices, it may occur that the folds are incorrectly formed resulting in conditions which deviate from those present in properly formed folds and in additional hollow spaces which make fusion welding impossible.
It is, therefore, the primary object of the present invention to provide welding seams effected by fusion weldings for the mechanical strengthening and/or sealing of folds in such a way that the manufacture of a strengthening and sealing welding connection is ensured even if the folds are formed in a manner deviating from the conventional.